The general long-term objectives of this project are to produce developmental quantitative genetic models that facilitate understanding of the original, development and evolution of complex traits. In this next period of the project, we propose to: Describe the genetic architecture of a suite of polygenetic traits in strains of mice genetically selected for early and late rate of development in body weight. Use analyses of conditional epigenetic variance to estimate the time of gene activity in various quantitative genetic traits in these mouse selection lines. Evaluate the role of uterine maternal effects of lifespan in various of the selection lines.